Dosage control apparatus

ABSTRACT

The invention is directed to a dose control apparatus. The apparatus has two armatures pressed against a valve seat by at least one spring. A coil induces a magnetic field that motivates the armatures against the force of the spring, thereby opening the valve. The armatures may move along a common axis in opposite directions. The apparatus may also include a core located between the armatures and a casing about the coil. The core and casing act to guide the magnetic field, reducing the power requirements for creating the field. Current may be periodically reversed in the coil to provide a degaussing field. In addition, a signal may be produced by the coil in the presence an externally applied magnetic field such as an MRI. An opposing magnetic field may be produced by the coil or the current provided to the coil may be adjusted.

RELATED APPLICATIONS

[0001] This application claims priority of U.S. patent ApplicationSerial No. 60/412,365, filed Sep. 20, 2002 entitled: “Programmable FlowController”, and is incorporated herein by reference in its entirety.

TECHNICAL FIELD OF THE INVENTION

[0002] This invention, in general, relates to an implantable drugdelivery system. More specifically, this invention relates to a dosecontrol system and valves used to manipulate the delivery rate of apharmaceutical solution.

BACKGROUND OF THE INVENTION

[0003] Implantable drug infusion therapy has been used to treat variousailments including pain management and diabetes. These drug pumps anddelivery systems have been used to deliver pain medication, hormonessuch as insulin, and other pharmaceutical agents. For example,intraspinal drug delivery may be used to treat chronic pain. Byutilizing these systems, pharmaceutical agents are delivered inrelatively lower doses to a specific region of treatment. In thismanner, full body dilution and membrane barriers are avoided. Similarly,insulin may be delivered without the inconvenience of injections.

[0004] Infusion pumps come in several varieties. Some infusion pumps areconstant rate such as those driven by gas pressures or springs. Othersare variable rate pumps driven by hydration of an expandable substanceor a variable rate pumping mechanism.

[0005] Implantable drug delivery systems have several advantages overexternal drug pumps, oral medications, suppositories, and injections.These implantable systems are unobtrusive, unencumbering, and typicallydeliver smaller doses to targeted regions. Pills, suppositories, andinjections deliver large doses of pharmaceutical agents that passthrough a large portion of the body to reach the treatment area. Thelarge dilution ratio caused by this passing requires a large dose toachieve an effective concentration in the treatment area. In addition,patients must remember to administer the correct dose at the appropriatetime to achieve the desired therapeutic levels of the pharmaceuticalagent in the treatment area.

[0006] While external infusion pumps overcome some of the limitations ofpills, injections, and suppositories, they are often cumbersome andinconvenient. These devices must typically be worn or strapped to thepatient, encumbering clothing selection and presenting a risk of damageto the external pump. In addition, catheter incision points are subjectto infection.

[0007] However, current versions of implantable infusion pump systemsalso have disadvantages. Typically, implantable infusion pump systemsprovide limited programmability and patient control. In addition, accessto the pump system is limited. Some pump systems have a constant ratewhile others attempt to control flow rates by varying pump speeds orhydration rates. In the case of constant rate pumps, prescription ratesare set by the selected flow restrictor and pump pressure. In the caseof variable rate pumps, prescriptions are limited by the available ratesettings associated with the pump.

[0008] Patients generally have no control over the prescription. In painmanagement cases, this can lead to periods of under dosing and periodsof unnecessary over treatment. Doctors are also limited in the selectionof prescriptions and often must have an office visit with patients toadjust prescriptions. These adjustments are expensive to insurancecompanies, unprofitable for doctors, and inconvenient for patients.

[0009] In the case of other treatments such as insulin treatment, therequired prescription varies with the behavior and environment of thepatient. Insulin requirements increase with carbohydrate laden meals anddecrease with activity. Excess insulin can lead to shock and low insulincan lead to excess blood sugar levels and many long-term healthproblems.

[0010] Another problem with implantable infusion pumps is determiningactual dosage rates and predicting reservoir levels. Limited access tothe pump means expensive preemptory refilling. Typical implantableinfusion pumps do not maintain rate data useful in determining actualdosage schedules and reservoir levels. Therefore, doctors havedifficulty predicting reservoir levels. This often leads to wastedpharmaceutical solution. Worse, the reservoir may empty and patents maysuffer from a lack of treatment.

[0011] A further problem with current dose control systems lies in theirmethod for controlling dose rates. These methods often use manymechanical parts that may wear. Further, these systems use parts thatmay malfunction under externally applied magnetic fields such as thoseof an MRI.

[0012] As such, typical infusion pumps suffer from deficiencies inproviding prescription options, actual prescription rate data, andcontrol of dosage. Many other problems and disadvantages of the priorart will become apparent to one skilled in the art after comparing suchprior art with the present invention as described herein.

SUMMARY OF THE INVENTION

[0013] Aspects of the invention may be found in an apparatus forcontrolling the flow of a treatment solution. The apparatus includes ahousing surrounding an enclosure and having two ports in communicationwith the enclosure. Each port has a valve seat surrounding the portopening. Further, each port has an associated armature with head pressedagainst the valve seat by a spring. At least one coil is used to createa magnetic field, which generates a force opposing the spring force,thereby opening the valve. In one case, the spring is the same springpressing both armature heads against the valve seats. The armatures mayhave a common central axis and move along this axis in oppositedirections. A core or spring stop assembly may be placed between thearmatures. A covering of magnetically permeable material may be placedabout the coil. The core and covering may be used to direct the magneticfield.

[0014] The coil may also be used to measure a signal response indicativeof an external magnetic field. A flow control module may implement inthe coil a signal that induces a magnetic field to oppose the externalmagnetic field or a degaussing field.

[0015] Additional aspects of the invention are found in a method forcontrolling the flow rate of a treatment solution. A valve is providedwith two armatures pressed against valve seats by at least one spring. Acoil is activated to induce a magnetic field that motivates thearmatures to move against the force of the spring and open the valve.The method may further include interpreting a signal from the coil toascertain the presence or strength of an externally applied magneticfield. A signal may be sent to the coil to induce an opposing field or adegaussing field.

[0016] As such, a dose control apparatus is described. Other aspects,advantages and novel features of the present invention will becomeapparent from the detailed description of the invention when consideredin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] For a more complete understanding of the present invention andadvantages thereof, reference is now made to the following descriptiontaken in conjunction with the accompanying drawings in which likereference numbers indicate like features and wherein:

[0018]FIGS. 1A and 1B are schematic diagrams of the system, according toone embodiment of the present invention;

[0019]FIG. 2 is a schematic block diagram depicting a dose controlmodule for use by the system as seen in FIG. 1A;

[0020]FIGS. 3 and 4 are schematic block diagrams depicting exemplaryembodiments of a dose control module as seen in FIG. 2;

[0021]FIGS. 5, 6, 7, and 8 are block flow diagrams depicting exemplarymethods for use by the dose control module of FIG. 2;

[0022]FIGS. 9A, 9B, 9C and 9D are schematic diagrams depicting anexemplary embodiment of a valve for use in the system as seen in FIG.1A;

[0023]FIGS. 10A, 10B, 10C and 10D are schematic block diagrams showinganother exemplary embodiment of a valve for use in the system as seen inFIG. 1A;

[0024]FIG. 11 is a schematic diagram depicting a further exemplaryembodiment of a valve for use by the system as seen in FIG. 1A;

[0025]FIG. 12 is a block flow diagram depicting an exemplary method foruse by the system as seen in FIG. 1A;

[0026]FIGS. 13, 14, and 15 are schematic diagrams depicting an exemplaryembodiment of a valve for use by the system as seen in FIG. 1A;

[0027]FIG. 16 is a graph depicting an inductance field resulting from apulse signal for use by the valve as seen in FIGS. 13, 14, and 15;

[0028]FIG. 17 is a schematic diagram of a circuit for producing theinductance field of FIG. 16;

[0029]FIG. 18 is a block flow diagram depicting an exemplary method foruse by the system as seen in FIGS. 13, 14, and 15;

[0030]FIG. 19 is a schematic diagram of a circuit for use by the systemas seen in FIG. 1A; and

[0031]FIG. 20 is a block flow diagram of an exemplary method for use bythe system as seen in FIG. 1A.

DETAILED DESCRIPTION OF THE INVENTION

[0032] Implantable drug treatment therapy is useful in treating avariety of ailments such as chronic pain management, insulin-dependentdiabetes, chemotherapy (systematic and targeted), Myelin treatment, andneurotransmitter treatment, among others. In each of these examples,patients could benefit from greater variety of prescriptions, morecontrol, and accurate monitoring of reservoir levels.

[0033] For example, in the case of pain management, patients may benefitfrom selectively applying various doses based on need. A preset array ofprescription levels would permit the patient to adjust treatment basedon pain, increasing as needed and decreasing otherwise. Limits and otherconditions may be established to prevent over dosing. Such a systemwould permit a patient to compensate for developing tolerances oradvancing pain.

[0034] Patients can also benefit from having more than onepharmaceutical agent or treatment solution delivered to the treatmentarea. Differing rate of drug delivery for different drugs can beeffective for pain management. For example, one pharmaceutical agent maybe infused for low-level pain while another is introduced only duringextreme pain. In this manner, tolerance development may be moderated forthe stronger drugs, or rates may be varied for those that are moreexpensive.

[0035] Similarly, treatments such as insulin treatments may be managedmore effectively with more patient control and multiple treatmentsolutions. For example, a patient may modify dose with activity andconsumption. Further, agents with varying time-release patterns,co-factors, and supplements may be introduced with varying rates.

[0036] Such a delivery pattern is realized with a separate dose controlsystem. FIG. 1A depicts an embodiment 1 of the present invention. Apressurized drug cavity 2 delivers a treatment solution through a filter3 and flow restriction 4 to valves 5 and 6. However, various motivatingsystems may be envisaged for supplying valves 5 and 6 with treatmentsolutions. The circuitry 7 using energy from battery 8 manipulates thevalves 5 and 6 to produce a flow rate in accordance with a prescription.However, one, two, or more valves may be used. The treatment solutionmay then travel through a catheter 11 to a treatment region in apatient. A bolus cavity 9 may be located inline to provide for theadministering of bolus dosages.

[0037] The circuitry 7 and battery 8 comprise a dose control module andmay be located separate from other elements as denoted by the enclosure13. However, other elements such as the valves 5 and 6 may be includedwith the circuitry 7 and battery 8 as indicated by the enclosure 15. Thebolus cavity 9 may also be enclosed with the circuitry 7 and battery 8.The drug cavity 2, filter 3, and flow restriction 4 may be located in aseparate housing.

[0038] Moreover, various valve configurations may be envisioned. Valves5 and 6 may be placed in series, parallel, or other arrangements. One,two, or more valves may be included in addition to restrictions toformulate various configurations.

[0039]FIG. 1B shows another embodiment 10 of the present invention. FIG.1B has an infusion pump 14 implanted in a patient 12. From the infusionpump, a catheter 20 leads through a dose control module 18 to atreatment area 22. The dose control module 18 may have a valve set 16 orother means of directing dosage. Alternately, the dose control module 18may have a communication link 26 with the infusion pump 14 or valve setthat aids in controlling dose. The system may also include an externalpatient control unit 24. The external patient control unit may directthe dose control module 18 to change dose rates or prescriptionconfigurations. In addition, other infusion pumps 28 may be connectedwith the dose control module 18 or valve set 16 such that multiplepharmaceutical solutions are delivered through the catheter 20 to thetreatment area 22.

[0040] The system may be useful in treating various ailments. Forexample, the treatment area 22 may be intraspinal. The infusion pump 14may deliver a morphate or other pain modifying pharmaceutical solutionsthrough the dose control module 18, valve configuration 16, and catheter20. In another case, the infusion pump 14 may deliver insulin through adose control module 18 and catheter 20 to be absorbed by thebloodstream.

[0041] The patient control unit 24 may be used to modify dosage toeither control pain in the case of a pain medication or control bloodsugar in the case of insulin delivery. For example, the patient controlunit 24 may permit the patient to select a prescription from a presetarray of prescriptions which is then transmitted the dose control module18.

[0042] A separate dose control module 18, as shown, provides aninterchangeable, flexible, dose control solution for implantable druginfusion therapy. Doctors may select a dose control module based on theprescription range, while using a pump with a constant flow rate.Surgeons may also implant multiple infusion pumps and connect them to asingle dose control module. In addition, doctors may establish a set ofprescriptions selectable by a patient and observe actual dosage rates.

[0043] To manipulate dosage rate, the dose control module 18 sends timedependent signals to dose or flow manipulating devices such as valvesand pumps, among others. A desired dosage rate may be achieved byopening a valve for a specific period of time. Alternately, the signalmay open and close the valve such that a time averaged dose rate isachieved.

[0044]FIG. 2 depicts an exemplary dose control module 30. Within ahermetically sealed housing, the dose control module 30 may have aprocessor 32, instructions 34, prescription settings 36, a flow meter38, a clock 40, a control circuitry 42, a communications interface 44, adata storage 46, security instructions 48, a power supply 50, dosemanipulators 52, and dose manipulator state sensors 54, among others.However, these elements may or may not be included. Further, they may behoused together, separate or in various combinations, among others.

[0045] Processor 32 functions to interpret instructions 34 in view ofprescription settings 36 and other data 46. The processor 32 interactswith control circuitry 42 to establish dosage rates and dose pathsthrough the valves and restrictors 52. The instructions 34 are softwareinstructions for implementing the various methods used by the dosecontrol module 30 and may include instructions for establishing valveconfigurations, determining the dose rate, calculating effectivestrength, determining dosage, comparing dosage to predetermined limits,determining valve position, and communicating with other devices, amongothers.

[0046] The prescription settings 36 take the form of parametersassociated with a prescription. These parameters may include dose rates,degradation rates, model parameters, limits, and conditions, amongothers. For example, a prescription setting 36 may be a dose rate of 0.8milliliters per day, with further limits of three hours at that rate fora limit of 0.3 milliliters over any given 12 hours. In another example,the prescription rate may be expressed in μg/day with a degradationmodel to determine a corresponding dose rate. However, various doserates, limits, and conditions may be associated with various therapies.

[0047] The dose control module 30 may include a flow meter 38. The flowmeter 38 may take various forms including a pressure drop sensor, arotary meter, a switch, and a force meter, among others. Alternately,the flow meter may calculate flow rates from known pump rates and valvepositions.

[0048] The system may also include a clock 40. The clock 40 may be usedin creating timed signals for manipulating dosage rates. The clock 40may also be used for determining whether dosage has exceeded thepredetermined limitations. Further, the clock 40 may be used to recordtime stamped data. The clock 40 may be used to determine time of day,time differences, and total time implanted, among others. With the clock40 and the flow meter 38, actual dosage data may be recorded, limits andconditions tested, and reservoir levels calculated. The benefits includean understanding of dosage rates, better prediction of reservoir levels,and more accurate adherence to overdose safety limits. Additionalcounters may be used to count fills and other parameters.

[0049] The control circuitry 42 is used to establish valve position ordose rates. This is accomplished by selectively sending signals to dosemanipulators such as valves and pumps. The processor in accordance withthe instructions 34 and the prescription settings 36 directs the controlcircuitry to create signals, manipulating valve position to control doserates.

[0050] The communications interface 44 may take various forms includingan interface with an external computer prior to implanting, or aradiofrequency interface to external devices. With a connection to acomputer, the dose control module 30 may be programmed and configuredprior to implanting. Once implanted, a doctor may interface with thedevice to establish prescription settings 36, download or upload otherdata from the data storage 46, and determine reservoir levels, amongother data. With a patient control unit, a patient may choose aprescription selected from a set of prescriptions preset by thepatient's doctor.

[0051] The dose control module 30 includes a data storage 46. The datastorage 46 may store time-stamped dose data, dosage data, otherparameters associated with valves, restrictors and device configuration,calculated reservoir levels, and other data. The data storage may takethe form of various RAM or flash memories, among others. The data mayalso be transmitted and stored on a patient control unit.

[0052] The dose control module 30 may also include security instructions48. These security instructions can include encryption algorithms orauthentication methods such as device identification numbers to limitaccess to the functionality of the dose control module 30.Communications with unauthorized devices may be ignored or limited intheir access to alter prescriptions.

[0053] The power supply 50 may take the form of a battery. The powersupply may also include a means of recharging from an externally appliedRF signal. The system may also monitor the power supply 50. If the powersupply 50 reaches a low level or power is lost, the system may includefail-safe electronic circuitry that could place the valves in a safeposition or the valve design can default to a safe configuration priorto the loss of power. For example, a reserve power supply or capacitormay direct the closing of all valves.

[0054] The dose control module may also include dose manipulators suchas valves and restrictions. These dose manipulators may be arranged invarious configurations to provide a variety of dosage rates andprescription configurations. Using various valve configurations, thedose control module may also deliver more than one drug, implement bolusinfusions, and permit a variety of pharmaceutical delivery rates to oneor more catheters. However, the valves may also be located external tothe dose control module 30.

[0055] The dose control module 30 may also include position sensors 54for determining the position of valves or state of dose manipulators 52.Alternately, the dose control module may use signals produced by thecontrol circuitry 42 and processed by the processor 32 to determine thevalve position. For example, signal response from an inductance coil maybe used to determine the position of a valve core.

[0056]FIG. 3 depicts another embodiment of a dose control module 76. Thedose control module 70 includes a microprocessor 72. The dose controlmodule 70 may be programmed using a programming module 74. Instructionsfor the microprocessor may be stored in the programming memory 76 andprescription parameters may be stored in the memory 78. Alternately,instructions may be received through the receiver/transmitter 82.

[0057] The program memory 76 may take the form of ROM, RAM, or flashmemory, among others. Similarly, the memory 78 may take the form of ROM,RAM or flash memory, among others.

[0058] The system may also include a clock 80 for time stamping data,determining whether dosage limit conditions have been met, and producingtime sensitive signals, among others. For example, the clock may be usedin creating an electromagnetic pulse signal for maintaining a minimummagnetic field about an inductance coil. The clock can also be used indetermining a dosage ratio or total dosage for comparison with limitsand conditions.

[0059] The power supply module 84 may provide power to themicroprocessor. Further, it may be used on conjunction with a voltagemultiplier 86 to control valve position. In accordance with theprescription parameters and the instructions stored in the programmemory, the microprocessor 72 may provide electromagnetic signals tovalves, directing the opening and closing of those valves using a pulseamplitude and width controller 88 and switch matrix 90.

[0060] The dose control module may be housed in a module, separate froma pump and reservoir. Valves, restrictions, and other dose manipulatorsmay be included in the module or housed separately. In this manner, asingle dose control module may manipulate dose rates associated withmore than one pharmaceutical solution and/or multiple valves to achievea selected prescription.

[0061] The patient control unit may have a circuitry similar to thatshown in FIG. 3. The patient control unit may have a processor, variousmemories, a clock, a receiver/transmitter, a power supply, and aprogramming modulator interface. With these elements the patient controlunit may communicate prescription selection and other data with the dosecontrol module.

[0062]FIG. 4 depicts an exemplary valve array 110. The electronics 112and the dose control module communicate through one or more controllines 114 to a set of valves 118, 120, 122 and 124. The system may alsoinclude various restrictors 116 and 126.

[0063] In this exemplary embodiment, a therapeutic solution enters theinlet and may pass through a restriction 116 if one is in place. Thevalves are configured to deliver the desired dose rate through theoutlet catheter 128. The valves may be configured in parallel usingvalves 118 and 122. Alternately, the valves may be configured in seriesusing valves 118 and 120. Further, the valves may be configured invarious complicated arrangements.

[0064] For example, if two 0.4 ml/day valves or restrictors separated byvalves are placed in parallel, the resulting flow would have a maximumof 0.8 ml/day depending on the pump's capacity. On the other hand, thetwo valves or restrictors, in series would yield a lower flow rate.

[0065] Various configurations of valves and restrictors may beenvisioned. Configurations may be envisioned that permit multipletherapeutic solution inlet points delivered to a single outlet, a singleinlet to multiple outlets, and various combinations. Furtherconfigurations may be envisioned that permit a variety of dose options.

[0066]FIG. 5 depicts an exemplary method for use by the dose controlmodule. The method 130 begins with the establishment of a prescriptionor a set of prescriptions as seen in block 132. A surgeon may establishthe prescriptions before or during the surgery using a computer.Alternately, the prescriptions may be established using an RF signaldevice after implanting. Access to the prescriptions may be varied bytime of day, reservoir levels, bolus limitations, time-out periods, andaverage dose limits, among others.

[0067] Once implanted, the dose control module may permit the patient toselect a prescription as seen in block 134. The selection of aprescription may, for example, be to initiate a bolus injection orselect from a preset set of dosage rates. The patient may activate anexternal control unit and transmit the desired prescription parametersto the dose control module. The prescription parameters may include dosetype, dose rate, drug type, limits, and duration, among other data.

[0068] The dose control module then determines whether the selectedprescription is permissible as seen in block 136. Permissibility of aprescription may be a function of dosage limits, reservoir availability,and other limits and conditions included as part of the prescription setby a doctor. If the selected prescription provides dosage rates abovethe prescribed limit, the system ignores the selection as seen in block139. Alternately, if the selection is permissible, the dose controlmodule may implement the prescription as seen in block 138. To implementthe prescription, the dose control module configures the valves inaccordance with the prescription settings and other parameters.

[0069]FIG. 6 depicts another exemplary method 140. The dose controlmodule receives a request for a new dosage as seen in block 141. Therequest may be received from a patient control unit or may bepreprogrammed in the dose control module. The dose control module maytest the request to determine whether it complies with dosage rules asseen in block 142. These dosage rules may include limits on averagedose, periods between bolus treatment, and time of day restrictions,among others. If the request does not comply, the control unit may applya default dosage as seen in block 148.

[0070] However, if the request does comply, the system may determine howto implement the dose. This determination may include determining thestrength of the treatment solution in the reservoir as seen in block143. The strength of solution may be affected by degradation, initialconcentration, time in place, and other factors. For example, the dosecontrol unit may determine the effective concentration of a treatmentsolution using a degradation model and then implement a flow rate thatprovides the requested dose as seen in block 144. However, thedetermination may be made before the compliance test or at other stepsin the method.

[0071] Once the dose is implemented, the dose control module monitorsthe length of time the dose has been implemented. This may includestoring a start time and comparing a clock value to the start time.Alternately, a timer may be started as seen in block 145.

[0072] Periodically, the system may confirm the request with an externalpatient control unit as seen in block 146. If the patient control unitconfirms the request, the timer may be restarted or a new initial timerecorded.

[0073] However, if the patient control unit does not respond or the unitdoes not confirm the dose, the dose control module may determine whethertime has expired on the does as seen in block 147. If time has notexpired, the dose control module may again seek to confirm the dose. Ifthe time expires, the module may return to a default dose as seen inblock 148.

[0074]FIG. 7 is another exemplary method 156 for use by the system. Datais received as seen in block 157. The clock is then accessed in block158. The clock may provide a time and date for comparison with storedtimes or may provide a period since refilling. These times are thenapplied in a degradation model as seen in block 159. However, variousparameters may be used in a degradation model including model constants,stored values, and reservoir condition data, among others. From thedegradation model, the system may determine a strength of the treatmentsolution and implement a dosage as seen in block 160. For example,application of the degradation model may provide an effective strengthof the treatment solution. A flow rate may be implemented that complieswith the dose.

[0075]FIG. 8 depicts a further method 150 for use by the system. Apatient control unit receives data from a dosage control module as seenin block 151. The data may include flow rate or dosage data, parameters,and prescription options, among others. The data is stored in thepatient control unit as seen in block 152. Operations may then beperformed on the data. With flow rate data, the patient control unit maydetermine a level in a treatment solution reservoir as seen in a block153. If the level is below a threshold as determined in block 154, thepatient control unit may alert a patient or medical professional as seenin block 155. However, various operations may be envisaged and theresult of these operations may be transmitted and/or stored in thedosage control module.

[0076]FIGS. 9A, 9B, 9C and 9D depict an exemplary embodiment of a valvefor use by the system. The valve is enclosed in a hermetically sealedexterior housing 180. An interior housing 170 surrounds an interiorenclosure or chamber 167. The valve has an inlet port 163 and an outletport 165. The inlet port 163 and outlet port 165 connect to the interiorchamber 167. Inside the interior chamber 167 is a core, armature, orplunger 169, which may include magnetic material. The core 169 mayinclude channels 162 that permit fluid to pass by the core 169 when thecore is in the open position. The core 169 also includes heads 171 and166. FIGS. 9A and 9B depict the valve in a closed position. In theclosed position, head 166 rests on seat 168, effectively blocking theoutlet 165.

[0077] Outside of the interior chamber 167 and interior housing 170reside magnets 178 and 172 and coils 174 and 176. When anelectromagnetic signal is directed through connectors 182 and 184 andwires (not shown) to the coils 174 or 176, one of the coils 174 or 176induces a magnetic field causing movement of the core 169. For example,if the core 169 is in the closed position as shown in FIGS. 9A and 9B,the coil 176 may be activated, inducing a magnetic field which draws thecore 169 away from magnet 172 and into the open position. The core 169may be held in the open position by magnet 178 once the coil 176 isdeactivated

[0078] The hermetically sealed exterior housing 180 and the interiorhousing 170 may be made of non-magnetic material. The exterior housing180 and interior housing 170 may be formed of mu-metal, non-magnetictitanium, ceramic, polymer, and other compounds. Mu-metal providesprotection against external electromagnetic fields such as thoseproduced by MRIs. The system may also counteract the electromagneticfields by producing an opposing field using the coils 174 and 176.

[0079]FIGS. 9C and 9D depict the valve in the open position. To movefrom the closed position to the open position, coil 176 may be activatedcreating a greater magnetic attraction near the inlet 163. The core 169then moves towards the inlet 163. The coil 176 may then be deactivatedand the magnet 178 holds the core in place. Fluid then travels throughchannels 162 and 164 into the chamber 169 and through the outlet 165. Toclose the valve, the coil 174 may be activated, creating a greatermagnetic field closer to the outlet, drawing the core 169 back to theclosed position. Magnet 172 holds the core in position. In this manner,the position of the core may be cycled to produce the desired dosagerate with minimum energy usage.

[0080] The permanent magnets 172 and 178 hold the core 169 in position.These permanent magnets 172 and 178 also provide a redundancy protectionin the case of mechanical shock to the system. In the event of shock orchange in gravitational forces, the magnets 172 and 178 hold the core inthe set position. The magnets 172 and 178 also resist fluid pressuresfrom altering the position of the valve core 169.

[0081] The seat size of the valve may also be important for reducingunwanted movement of the core. If the seat size is small enough, thepump pressure experienced by the core when proximate to the inlet portwill exert a force less than that exerted by the magnet holding the corein place.

[0082] However, various configurations of seats may be envisioned. Seatsmay be positioned about both inlets such that fluid only flows while thecore is in a transient position. In another example, the inlet andoutlet may be reversed.

[0083] For the configuration shown, the pump pressure will influence thevalve to stay in a closed position in the event that power isunavailable or either of the magnets is damaged. Alternately, if a failopen valve is preferred, a valve seat may be placed on the inlet and thedose channels placed about the outlet. The pump pressure would theninfluence the core to remain in the open position if power isunavailable.

[0084] An alternate embodiment may be seen in FIGS. 10A, 10B, 10C and10D. In the embodiment shown in FIG. 10A, the magnet 203 is positionedabout a port 192. Coils 208 and 210 may be alternately activated to movethe core 198 into the open position near port 192 or into the closedposition near port 194. In the closed position, a head 200 may rest onthe valve seat 206, effectively closing off flow.

[0085] The core 198 may take various forms. The core 198 may be madefrom magnetic material. This material may include paramagnetic material.In which case, the coils and magnets would pull the core 198 intoposition. Alternately, the core 198 could be composed of diamagneticmaterial. In which case, the core 198 would be pushed into position bythe magnets and coils. The core 198 may also be made from compositematerials that include magnetic material such as Teflon-coatedferromagnetic materials, among others. Alternately, the core 198 may bemade of a non-magnetic material with magnetic rods or a secondary coreinside.

[0086] The head may take various forms. These forms may include siliconeand other biocompatible materials suitable for fitting snug against avalve seat.

[0087] As seen in FIG. 10B, the core 198 may have channels 202 and ahead 200. In the closed position the head 200 may rest against a valveseat. However, in the open position, the channels 202 may permit fluidto flow around the core 198 and through the outlet. FIG. 10C shows analternate embodiment in which the channels 216 may be drilled throughthe core 214. In this case, the core 214 has a head 212 that rests onthe valve seat in the closed position.

[0088] However, various seats and core styles may be envisaged. Forexample, FIG. 10D shows a triangular core 222 that may be positioned ina cylindrical chamber. The triangular core may have a head 220 thatrests on a valve seat effectively closing the valve. However, when open,fluid may pass around the edges of the triangle with little restriction.Alternate embodiments may include a spherical core in an enclosure witha square cross-section. In this example, the sphere may be a siliconecoated ferromagnetic sphere. However, many embodiments may beenvisioned.

[0089]FIG. 11 depicts a further embodiment of the valve 230 as a core238 in a chamber 236. The valve has a bellows 252. Coils 248 and 250 maybe cycled on and off to move the core 238 through the chamber 236. Whenthe core 238 rests on valve seat 246, the bellows 252 may fill with thepharmaceutical solution. Alternately, when the core 238 and the corehead 242 rest against valve seat 244, the bellows 252 may drain throughthe outlet 232. One advantage to this system is that the maximum dose apatient can receive in the event of valve failure is equal to the volumeof the bellows 252.

[0090] In a similar embodiment, one end of the chamber may have channelsinstead of a valve seat. The core 238 may be positioned at that end andpermit fluid flow. In this case, the bellows will act to controlpressure fluctuations or spread out the drug delivery.

[0091] Dosage control systems including the valves of FIGS. 9, 10, and11 have another advantage in that the valve position may be determinedthrough the response of the coils to signals. If the core is positionednear the coil, the signal will represent a different inductance than ifthe core is further from the coil. In this manner, the system maydetermine valve position and in the event of error, attempt toreposition the valve, stop flow from the pump, or alert the patient,among others.

[0092]FIG. 12 depicts an exemplary method for operating the valve. Themethod 270 involves energizing the coil 272 to move the valve positioninto the desired position. The dose control module may then test todetermine whether the core is in the correct position by sending asignal through one or the other coils as seen in block 174. Thereturning signal will vary in accordance with the inductance caused bythe presence of the core. The dose control module may then analyze thesignal as seen in block 276 to determine the position of the core.Alternately, the system may test and analyze the signal prior toenergizing the coils. Further, the system may periodically test theposition of the core to ensure that the valve is in the appropriateposition and is functioning properly.

[0093] The coils may also be used to counteract external magnetic fieldssuch as those produced by an MRI. The MRI may induce a current in thecoils. This signal may be interpreted by a dose control module toascertain the direction and strength of the magnetic field. A signal maythen be sent to the coils to counteract or oppose the external magneticfield. In this manner, valve position may be ensured and damage to themagnets or the core prevented.

[0094] Another valve for use by the system may be seen in FIG. 13. FIG.13 represents a solenoid valve with dual armatures, wherein eacharmature may be opened by one or more coils. Valve 290 has two ports 292and 294. These ports connect to a housing forming an interior chamber.Each port has an associated valve seat, 302 and 314. Against these valveseats may be valve heads and armatures 304 and 312, respectively. Eachof these armatures is held in place by an associated spring 306 and 310,respectively. These springs, 306 and 310, may press against a springstop 308. Alternately, they may press against separate spring stops. Aspool 298 surrounds the enclosure. Coils 300 are wrapped around thespool 298. Activation of the coils 300 induces a magnetic field thatdraws the valve heads 304 and 312 away from their respective seats 302and 314 and towards spring stop 308. The armatures 304 and 312 may havea common axis of movement but move in opposite directions, toward thecenter of valve 290.

[0095] Fluid flow occurs from one port, i.e. inlet port 292, through theinterior chamber 316 and connecting chamber 320, and exists throughchamber 318 and outlet port 294.

[0096] The armatures 304 and 312 may be made of magnetic material. Headson the armatures may be made of silicone or a material capable ofsealing against the valve seats. The armatures may also have channels,grooves, or holes to permit fluid flow when the head is away from thevalve seat. The springs may be made of magnetic or non-magneticmaterial.

[0097] The hermetically sealed exterior housing 296 may be made ofnon-magnetic material. The exterior housing 296 may be formed ofnon-magnetic titanium, ceramic, polymer, and other compounds.

[0098] The valve system of FIG. 13 provides several redundancies. Havingtwo springs and valve assemblies ensures that if one valve assemblysticks open, fluid will still be prevented from flowing by the secondoperational valve assembly. If the valve experiences a directionalmagnetic field, one valve assembly might open, however, the other wouldremain closed. Further, if a leak across a seat causes pressure to buildin the interior of the valve, the pressure will force the valveassemblies against their seats, preventing unwanted leakage.

[0099] The design of the inlet size is also important. Smaller inletdiameters prevent leaks from the inlet port by reducing the total forceagainst the head. This smaller force may also permit smaller springconstants to be used, reducing the opening force requirements and thusthe power requirements of the coil.

[0100] An alternate embodiment may be seen in FIG. 14 in which a commonspring 344 presses the valve heads 342 and 346 against their respectiveseats. During the closed position, the coils 340 wrapped around spool338 may be activated to draw the valve heads 342 and 346 inward alongthe axis of flow, compressing spring 344. The single spring assemblyremoves the double spring redundancy and hence, the valve may beadvantaged by few parts for wear and tear.

[0101]FIG. 15 depicts a further exemplary embodiment of the valve asseen in FIGS. 13 and 14. Armatures 362 and 366 are pressed against valveseat associated with ports 352 and 354 with at least one spring 364. Acoil 360 may induce a magnetic force in the armatures 362 and 366 thatopposes the spring 364. A core 368 is located between the armaturesallowing for enough space to permit movement of the armatures sufficientfor permitting fluid flow, In addition, a cover 369 is located about thecoil. The cover 369 and the core 368 are made from materials that act toguide the magnetic field and in turn strengthen the effect of thecoil-induced magnetic field on the armatures 362 and 366.

[0102] These valves, shown in FIGS. 13, 14, and 15, have the advantageof being redundantly in a closed position. The valves also have theadvantage of alternately being in a closed position given a strongmagnetic field in one direction along the axis of the valve. Such astrong magnetic field may be experienced during testing, such as an MRI.

[0103] Moving the valves into an open position may require more energythan keeping the valves open. This is a product of theinductance-produced electromagnetic field. To open the valves, a largeramount of energy must be applied to the coil to produce a magnetic fieldstrong enough to open the valves. However, once the valves are open, themagnetic field may be maintained using less energy. As such, energy maybe conserved by reducing the current applied to the coils or providing atimed signal to the coils, among others

[0104]FIG. 16 depicts an exemplary embodiment of a timed signal. Theinduced magnetic field is represented by the line 0. To produce thismagnetic field, a signal A is directed to the coils. To open the valve,a longer duration pulse is provided to the coils causing the magneticfield to increase. Once the valve is open, the pulse stops, causing themagnetic field to gradually decrease. During this gradual decrease, acurrent signal B is produced in the coil. This signal may be used forregenerating power sources or recovering energy. In this manner, powermay be conserved. Once the magnetic field reaches a minimum, the signalA may produce another pulse, increasing the magnetic field. In thismanner, the valve may be kept open using a minimal amount of energy.Alternately, a larger powered pulse may be used to open the valve and aconstant low power signal to keep the valve open.

[0105]FIG. 17 depicts an exemplary circuitry 375 for producing thesignals of FIG. 16. An induction coil 377 is associated with a valve. Apower source 376 is coupled with the coil 377 through switches 378, 379and 380, and diode 381. The switches may take various forms includingvarious transistors, four-level diodes, relays, and thyristors, amongothers. The circuitry may also include an energy collection circuitry382. A controlling circuitry may be coupled to the switches. However,various modifications to this circuitry 375 may be envisaged.

[0106] If switches 378 and 379 are closed or activated, current flowsthrough the coil 377, inducing a magnetic field. Once the field isstrong enough, the valve opens. In one embodiment, the magnetic forceson the armatures in the valve overcome a spring force and open thevalve. After initially opening the valve, the switches 378 and 379 areused to produce electric pulses through the coil 377 to maintain themagnetic field above a threshold value below which the valve would closeor reseat.

[0107] Between pulses, the magnetic field motivates a current to flow inthe same direction as that used to induce the field. If switch 380 isclosed or activated, current is directed through the diode 381 towardthe positive end of the power source. Alternately, energy may becollected by an energy collection circuitry 382. This circuitry 382 isdepicted as a capacitor. However, it may take various forms.

[0108] Various additional switches, diodes and connections may be madeto permit periodic reversal of current for producing a degaussing fieldwith the coil 377. The system may also be grounded as seen in ground383. However, various modifications to the circuitry may be envisaged.

[0109]FIG. 18 is an exemplary method for use by the system. The method370 calls for energizing the coils as seen in block 372. This may beaccomplished by providing a higher amplitude pulse or a longer pulse toproduce the induced electromagnetic field. The coil may then be pulsedas seen in a block 374 to maintain the valve in an open position. Thepulsing may be used to reduce the energy requirement of the system.Further, between pulses, the induced voltage and current in the coil maybe used to recover energy.

[0110] The system may be subject to various strong externalelectromagnetic fields, as in the case of MRI testing. The valves ofFIGS. 9, 10 and 11 and those of FIGS. 13, 14, and 15 may undergo thesestrong magnetic fields when placed in a patient. It is thereforeimportant to counteract these strong electromagnetic fields to ensurefunctionality of the valve.

[0111]FIG. 19 depicts a circuit that may be used to counteract theeffects of a strong unidirectional electromagnetic field or produce adegaussing field. The system may test the coil 402 to determine thedirection of the electromagnetic field. Then, an opposingelectromagnetic field may be produced in the coil by applying thecorrect voltage or current. To produce current in one direction, theswitches 394 and 398 may be closed and the signal generator 392activated. To produce current in the opposite direction, and thus anopposite electromagnetic field, switches 396 and 400 may be closed whileswitches 394 and 398 remain open.

[0112] This circuitry may also be used to periodically change thedirection of current across a coil, effectively providing a degaussingfield. The circuitry of FIG. 17 may also be modified to recover power.The circuitry of FIG. 17 may be incorporated as part of signal generator392. Alternately, a modified circuitry may be placed about the coil 402.

[0113]FIG. 20 depicts an exemplary method 410. In this method, thesystem tests for the electromagnetic field induced by the external,directional electromagnetic field. The system then applies an opposingfield by sending a current in the appropriate direction through thecoils as seen in a block 414.

[0114] In this manner, an external electromagnetic field may becounteracted. For the dual-head solenoid type valve, a strongunidirectional field would attempt to open one side while exertingexcess pressure on the other side. Neutralization of the field wouldensure valve closure, reduce wear on valve parts, and preventmagnetizing the armatures. For the movable core valve, a strongunidirectional magnet field may place the core in an undesired position,damage the permanent magnets and magnetize the core, Here too, the coilsmay be used to neutralize the field, Simultaneously, some of an inducedcurrent in the coils could be used to regenerate power.

[0115] Both valve types may also benefit from a reverse currentperiodically applied to the coils. The reverse current would cause adegaussing of magnetism and prevent residual buildup of magnetism ineither the core or the armatures. Such a reverse current may be producedby the circuit of FIG. 19.

[0116] As such, a dose control module and valves are described. In viewof the above detailed description of the present invention andassociated drawings, other modifications and variations will now becomeapparent to those skilled in the art. It should also be apparent thatsuch other modifications and variations may be effected withoutdeparting from the spirit and scope of the present invention as setforth in the claims which follow.

What is claimed is:
 1. An apparatus for controlling dose rates of one ormore treatment solutions, the apparatus comprising: a body surroundingan interior chamber, the body having a first and a second port, each ofthe two ports having an associated port opening in communication withthe interior chamber and an associated assembly comprising: a valveseat; an armature having a head, the head associated with the valveseat; and a spring engaging the armature with a spring force directedthe head against the valve seat; and at least one coil surrounding thebody, the coil operable to induce a magnetic force in the armaturesopposing the spring force, thereby opening the valve.
 2. The apparatusof claim 1, wherein the armatures associated with the two ports have acommon movement axis and travel along the common movement axis inopposite directions.
 3. The apparatus of claim 1, wherein the springassociated with each of the two ports is a common spring.
 4. Theapparatus of claim 1, wherein an electric pulse is directed through theat least one coil, thereby inducing a magnetic field that motivates thearmatures toward the open position.
 5. The apparatus of claim 1, whereina series of electric pulses are directed through the at least one coil,thereby inducing a magnetic field that influences the armature to remainin the open position.
 6. The apparatus of claim 1, wherein, under anexternally applied magnetic field, the at least one coil emits a signalassociated with the externally applied magnetic field.
 7. The apparatusof claim 6, wherein the at least one coil receives a signal inducing amagnetic field opposing the externally applied magnetic field.
 8. Theapparatus of claim 1, further comprising a core located within theinterior chamber and between the armatures.
 9. The apparatus of claim 1,further comprising a casing about the at least one coil, the casinginfluencing the magnetic field induced by the at least one coil.
 10. Theapparatus of claim 1, wherein the direction of current in the at leastone coil is periodically reversed to inducing a degaussing field.
 11. Anapparatus for controlling dose rates of at least one treatment solution,the apparatus comprising: a body surrounding an interior chamber, thebody having two ports, each of the two ports having a port opening incommunication with the interior chamber and an associated assemblycomprising: a valve seat; an armature having a head, the head associatedwith the valve seat; and a spring engaging the armature with a springforce directed the head against the valve seat; the armature of each ofthe two valves having a common movement axis and traveling along thecommon movement axis in opposite directions; at least one coilsurrounding the body, the coil inducing a magnetic force in thearmature, the magnetic force opposing the spring force, thereby openingthe valve; a magnetically permeable core located within the interiorchamber and between the armatures; and a magnetically permeable casinglocated about the coil and body.
 12. The apparatus of claim 11, whereinthe spring associated with each of the two ports is a common spring. 13.The apparatus of claim 11, wherein an electric pulse is directed throughthe at least one coil, thereby inducing a magnetic field that motivatesthe armatures toward the open position.
 14. The apparatus of claim 11,wherein a series of electric pulses are directed through the at leastone coil, thereby inducing a magnetic field that influences the armatureto remain in the open position.
 15. The apparatus of claim 11, wherein,under an externally applied magnetic field, the at least one coil emitsa signal associated with the externally applied magnetic field.
 16. Theapparatus of claim 15, wherein the at least one coil receives a signalinducing a magnetic field opposing the externally applied magneticfield.
 17. The apparatus of claim 11, wherein the direction of currentin the at least one coil is periodically reversed to induce a degaussingfield.
 18. A method for controlling the flow of a fluid, the methodcomprising: opposing two or more armatures within an interior chamber;placing one or more springs between the armatures, wherein the springsforce the armatures against an armature's associated valve seat;inducing a magnetic field with at least one coil, the magnetic fieldmotivating the armatures to move along a common axis in oppositedirections against the force of the one or more springs providing a pathfor fluid flow.
 19. The method of claim 18, further comprising:reversing, periodically, the direction of current flow through the atleast one coil to form a degaussing field.
 20. The method of claim 18,further comprising: measuring a response from the at least one coil todetermine the presence of an externally applied magnetic field.
 21. Themethod of claim 20, further comprising: inducing in the at least onecoil a magnetic field opposing the externally applied magnetic field.